Even with the cost of oil skyrocketing thanks to demand and global unrest, it's quickly being replaced by water as the most expensive commodity for homes and buildings, even with many of them relying on oil for heat.

And with the city proposing another increase in water rates - this time a 7 percent increase - that expense is only going to grow.

Since 2005, the city has increased water rates by 78 percent. If the new 7 percent increase goes into effect - the city Water Board is expected to vote on the proposal on May 4 - an average homeowner will see their water bill increase from approximately $877 per year to $939 per year.

That might not seem like a lot, but if you take into account the increases in water rates since 2005, then you find that that paying for water has quickly become one of the biggest expenses for homeowners.

Which doesn't even take into account large rental buildings and co-ops. A member of a co-op board that we spoke with said that expenses related to water rates increased from about $45,000 in 2010 to $85,000 in 2011. A huge increase in just over a year.

In the end, that expense is passed on to shareholders and tenants in rental buildings in the form of higher maintenance fees and rents.

Part of the problem is that the Department of Environmental Protection (DEP) pays hundreds of millions of dollars annually to the city's General Fund, which means that the money that you pay in water rates doesn't always go toward actually making the city's water and sewer system more efficient to prevent future cost increases, but is instead used to fix potholes and cover other budget shortfalls.

In fact, probably one of the biggest upgrade that DEP has undertaken in the past few years is getting more efficient at billing you and collecting that money.

So when the Water Board raises your water rates, don't necessarily expect the extra money to go toward fixing that flooding problem on your block or upgrading the water delivery system or implementing measures to conserve water.

Essentially, increases in water rates are a backdoor tax on property owners. And now the Water Board is considering increasing that tax again.

To their credit, DEP is making strides to eliminate waste, including embracing green infrastructure and working on a three-year plan to cap payments to the General Fund at $136 million annually.

That's all well and good, but the department should have been instituting these measures years ago when water rates began to increase at an out-of-control rate, not let the city siphon off the money it collected from residents to be spent on other projects.